The invention refers to a tappet for a valve actuating mechanism of an internal combustion engine having a circular ring shaped base section and a circular base section which are arranged concentrically to each other and respectively acted upon by cams of different strokes, with a central cam of small stroke acting upon the circular base section and at least one adjacent cam of greater stroke acting upon the circular ring shaped base section, wherein the tappet is guided in a bore of a cylinder head by a hollow cylindrical jacket that is connected to the circular ring shaped base section while the circular base section receives at its cam-distant end face a guide sleeve accommodating a clearance compensation element, and wherein the units which comprise the two base sections are slideable relative to each other and engageable by radially displaceable coupling means.
German Pat. No. DE-A-42 06 166 discloses a tappet of this type which includes a two-part housing with a base acted upon by at least two cams of different stroke pattern. Coupling of both housing parts is effected by pistons that act in radial direction and are provided with pins. In disengaged position, the outer housing part executes an idle stroke. The inner housing part follows the contour of the inner cam. The valve executes a smaller stroke. In case the tappet of this type should act hydraulically in order to compensate a possibly existing valve clearance, it is not possible or only at great difficulty to effect the oil supply to the hydraulic element. In this case, a second, separate oil supply conduit that extends from the cup-shaped jacket to the piston and to the clearance compensation element would be required in combination with separate control conduits within the cylinder head.
A further drawback of the tappet known from the above-mentioned publication is its lack of disclosing for both locking elements a limitation of axial displacement or a safety mechanism to safeguard a loss thereof. Moreover, as the base is of flat configuration, the external cam has only a limited support on the base for actuating the outer housing part. In order to ensure the area that is required during the migration of the cam on the base of the tappet, and to realize the desired valve lift diagrams, a base of cylindrical configuration in the camshaft direction would be desirable.